Radon is the one bunker hazard with no warning at all. It has no smell, no color and no symptoms, and below-grade rooms are exactly where it collects.
What radon is
Radon forms from the natural decay of uranium in soil and rock. It moves up through the ground as a gas and enters buildings through slabs, joints and penetrations. Outdoors it disperses. In a sealed room cut into the earth, it accumulates. The EPA calls radon the leading cause of lung cancer among people who have never smoked and estimates about 21,000 radon-related lung cancer deaths a year in the United States.
How common it is in Utah
The Utah Department of Environmental Quality reports that about 1 in 3 Utah homes tested had radon above the EPA action level, and 1 in 2 in some areas. The average in tested homes was 5.3 picocuries per liter, above the action level of 4. Those are ordinary houses. A bunker sits lower, in closer contact with the soil, with less natural air exchange.
What the numbers mean
Radon is measured in picocuries per liter of air (pCi/L). The EPA action level is 4 pCi/L, and the EPA suggests considering a fix between 2 and 4. There is no known safe level; lower is better. Because a family may spend weeks underground at a stretch, we aim to keep shelters well below the action level, not just under it.
How to test a bunker
Utah DEQ sells test kits for $10.95 through radon.utah.gov. A short-term test gives a first reading in days; a longer test averages out seasonal swings. For a shelter, test with the space closed up the way it will be used, test every sleeping area, and test again after any mitigation. A continuous electronic monitor is the best long-term answer, which is why our Standard and Premium air systems include one.
How mitigation works
The standard fix is sub-slab depressurization: a pipe through the slab and a small fan that pulls soil gas from beneath the floor and vents it outside, which can bring levels below 2 pCi/L. In an existing home, a certified contractor typically charges $1,000 to $2,000, and Utah DEQ puts the usual cost around $1,500. Sealing cracks alone does little. In a new shelter, the cheapest time to handle radon is before the slab is poured: a gas-permeable layer, a sealed membrane and a vent path, so a fan can be added if testing calls for it. Positive pressure from the filtered air system also helps keep soil gas out while it runs.
Read the wider list of why underground bunkers fail.
Key takeaways
- Radon is a radioactive soil gas that collects in below-grade space.
- Utah DEQ reports elevated radon in about 1 in 3 Utah homes tested, and 1 in 2 in some areas.
- The EPA action level is 4 pCi/L; consider a fix between 2 and 4.
- Sub-slab depressurization typically costs $1,000 to $2,000 in a home and is cheapest built in.
- Test before anyone sleeps underground, and again after mitigation.
This guide is general information to help you plan. It is not engineering, legal or water-rights advice, and requirements vary by state and county. Every Styrkholm project is designed by licensed professionals for the specific site.